CNC Engineering Glossary

A flat, dimensioned technical drawing — front, top, and side views plus tolerances and notes — used to fully specify a part for manufacturing and inspection.

CNC machining that moves a cutting tool along three linear axes — X, Y, and Z. It is the standard configuration used for most milling operations.

Three common austenitic stainless grades: 303 is optimized for machinability, 304 offers general-purpose corrosion resistance, and 316 adds molybdenum for superior resistance in marine or chemical environments.

A digital solid or surface representation of a part's geometry (commonly a STEP or IGES file) used for CAD design, CAM programming, and quoting.

3-axis motion plus a rotary axis (usually called the A-axis), letting the workpiece rotate so several faces can be machined without manually repositioning it.

Three linear axes combined with two rotary axes, giving the cutting tool access to complex geometries and undercuts in a single setup.

A heat-treated aluminum alloy valued for its balance of strength, light weight, corrosion resistance, and machinability. A common default choice for structural and enclosure parts.

A high-strength, zinc-alloyed aluminum grade often used in aerospace and performance parts. Stronger than 6061 but generally less corrosion resistant.

The intentional dimensional difference designed between two mating parts to produce a specific type of fit, such as clearance or interference.

A GD&T control that limits how far a surface or axis may deviate from a specified angle relative to a reference datum.

An electrochemical process that thickens the natural oxide layer on aluminum parts, improving corrosion resistance, wear resistance, and allowing the surface to be dyed a color.

A quality management standard built on ISO 9001 with additional requirements specific to the aerospace and defense industry.

A technical drawing that shows how individual machined components are positioned and fastened together to form a finished product.

The three mutually perpendicular directions of linear travel that define a CNC machine's coordinate system.

A structured list of every part, raw material, and quantity required to build a complete assembly.

A machining operation that enlarges and refines an existing hole to a precise diameter using a single-point cutting tool.

A copper-zinc alloy prized in CNC machining for its excellent machinability, corrosion resistance, electrical conductivity, and warm appearance.

A machining process that pulls or pushes a toothed tool through a workpiece in a single linear pass, commonly used to cut keyways and internal splines.

A raised edge or thin sliver of excess material left on a part after cutting, drilling, or milling. Burrs are normally removed during deburring.

A cylindrical liner, usually bronze or plastic, that reduces friction and wear between a rotating shaft and its housing.

Software used to create 2D drawings and 3D models that fully define a part's geometry before it is manufactured.

Software that converts a CAD model into toolpaths and CNC-readable G-code, telling the machine exactly how to cut the part.

An angled cut across a sharp corner or edge, used to ease assembly, remove sharpness, or reduce stress concentration.

The thickness of material each cutting edge removes per revolution of the tool — a key variable for tool life, cycle time, and surface finish.

A precision inspection instrument that uses a touch or optical probe to measure a finished part's exact geometry against its CAD model.

The automated control of machine tools through pre-programmed software, enabling fast, repeatable, high-precision manufacturing of metal and plastic parts.

A GD&T callout requiring the median points of a feature to fall within a cylindrical tolerance zone centered on a datum axis.

A fluid sprayed or flooded onto the cutting zone during machining to reduce heat, lubricate the tool-workpiece interface, and clear away chips.

The small rounded transition a cutting tool naturally leaves in an internal corner; sharp internal corners typically require EDM or a smaller-diameter tool.

A flat-bottomed, enlarged section machined at the top of a hole so a bolt head or washer can sit flush with or below the surface.

A cone-shaped recess machined at a hole's opening that lets a flat-head screw sit flush with the surrounding surface.

The total time required to complete one full machining operation on a single part, from tool engagement to completion.

A theoretically exact point, axis, or plane used as the reference from which the location and geometry of other features on a drawing are measured.

A finishing step that removes burrs left behind by machining, improving part safety, fit, and appearance.

The practice of designing a part so it can be produced faster, more reliably, and at lower cost — without compromising its function.

A metal-casting process in which molten metal is forced under high pressure into a reusable steel mold, well suited to complex parts in high volumes.

A precisely sized cylindrical pin pressed into mating holes to align two parts or maintain their position during assembly.

A slight taper added to the vertical walls of a molded or cast part so it can be released from the mold without damage.

A rotating cutting tool used to create round holes in a workpiece.

A process that removes metal using controlled electrical sparks rather than a cutting edge — ideal for very hard materials and intricate internal geometry standard tools cannot reach.

A rotary cutting tool used in milling to remove material from the sides, bottom, or profile of a workpiece.

A formal technical document that specifies a part's dimensions, tolerances, materials, and finish requirements for manufacturing.

Describes a material, coating, or surface engineered to dissipate static electricity and protect sensitive electronic components from damage.

A manufacturing process that pushes material through a shaped die to create a part with a constant cross-sectional profile, such as a bar or channel.

A milling operation that cuts a flat surface perpendicular to the rotating tool's axis, typically used to establish a flat reference surface.

The speed at which a cutting tool advances through the workpiece, usually measured in millimeters or inches per minute.

A rounded interior or exterior transition between two surfaces, used to reduce stress concentration and, on internal corners, to match standard tool geometry.

The texture and quality of a part's surface after machining, commonly measured as Ra, the surface roughness average.

A device that holds and precisely locates a workpiece during machining to guarantee repeatable accuracy across a production run.

A GD&T control that limits how far a surface may deviate from a perfectly flat plane.

A manufacturing process that shapes metal using localized compressive force, producing parts with improved grain structure and strength.

The standardized programming language that directs a CNC machine's tool movements, speeds, and tool changes.

A numbering system that indicates sheet metal thickness; counter-intuitively, a lower gauge number means a thicker sheet.

A symbolic language used on engineering drawings to precisely define the allowable variation in a part's form, orientation, and location relative to datums.

A finishing process that uses a rotating abrasive wheel to remove small amounts of material, achieving very tight tolerances or fine surface finishes.

A thicker, harder anodized coating than standard Type II anodizing, offering superior wear resistance and corrosion protection for demanding applications.

A material's resistance to localized permanent deformation, commonly measured on the Rockwell or Brinell scale.

A controlled process of heating and cooling a metal to alter its hardness, strength, or ductility.

A CNC toolpath strategy that combines circular and linear motion to cut a hole or thread in a smooth spiral rather than a straight plunge.

A low-speed abrasive finishing process used to achieve precise bore diameters and fine surface finishes, often on cylinder bores.

A process where molten plastic is injected into a mold cavity, cooled, and ejected as a finished part — typically used for medium- to high-volume production.

A document recording a finished part's measured dimensions compared against the drawing's specified tolerances.

The coordinated motion of multiple CNC machine axes to cut a straight line, arc, or complex curve.

An internationally recognized standard for quality management systems, widely used across manufacturing industries.

A standardized classification, from IT01 to IT18, describing how precise a dimensional tolerance is; lower numbers mean tighter tolerances.

A workholding device that not only secures a part but also physically guides the cutting tool during machining.

Manual, incremental movement of a single machine axis, typically used during setup or tool positioning.

The section of a rotating shaft that is supported by a bearing.

The width of material removed as a cutting tool passes through a workpiece, most relevant in sawing, laser, and waterjet cutting.

A slot machined into a shaft and its mating hub to house a key that transmits rotational torque between the two.

A machining process that presses or cuts a textured, repeating pattern into a surface, most often to improve hand grip.

A machine tool that rotates a workpiece against a stationary cutting tool — the foundation of CNC turning.

The total elapsed time between placing an order and receiving the finished parts.

Rotating tools mounted on a CNC lathe's turret that allow milling, drilling, or tapping operations without moving the part to a separate machine.

Manufacturing runs sized for smaller order quantities, often used for pilot builds and market testing ahead of mass production.

Machine-specific commands within a CNC program that control auxiliary functions such as coolant flow, spindle start/stop, and tool changes.

A material's relative ease of being cut, drilled, or finished with standard tooling, affecting tool wear, cycle time, and achievable finish.

A CNC machine capable of performing multiple operations — milling, drilling, tapping — in a single setup, often with an automatic tool changer.

Documentation from a mill or supplier confirming that a batch of raw material meets specified chemical composition and mechanical properties.

The science of measurement as applied in manufacturing to verify that part dimensions and tolerances meet specification.

A precision hand tool used to measure small dimensions to within thousandths of a millimeter or inch.

A machining process in which a rotating cutting tool removes material from a workpiece to produce flat surfaces, pockets, slots, and contours.

The predecessor to CNC, using coded instructions on punched tape or cards to control machine tool movement.

A part produced by casting, forging, or 3D printing that already closely matches its final dimensions, minimizing the machining needed to finish it.

Arranging multiple part outlines on a single sheet or block of raw material to minimize scrap and material cost.

A heat-treatment process that diffuses nitrogen into a metal's surface, increasing hardness and wear resistance with minimal distortion.

A precisely dimensioned channel machined into a part to house an O-ring and create a reliable seal.

A company that produces components or products that are marketed and sold by another company under its own brand.

A programmed compensation value that accounts for a cutting tool's exact length or diameter relative to the CNC machine's reference point.

A two-step molding process that forms a second material, often a soft plastic, over a rigid substrate part.

A GD&T control that requires a surface, axis, or line to remain equidistant from a reference datum plane or axis across its full length.

The visible seam on a cast or molded part where the two halves of the mold meet.

A chemical treatment for stainless steel that removes free iron from the surface, restoring and enhancing the part's natural corrosion resistance.

A high-performance engineering plastic known for excellent mechanical strength, chemical resistance, and stability at elevated temperatures.

A GD&T control that limits how far a surface or axis may deviate from a 90-degree angle relative to a reference datum.

Depositing a thin metallic layer — such as nickel, zinc, or chrome — onto a part's surface to add corrosion resistance, conductivity, or appearance.

A GD&T control that defines the allowable zone within which a feature's true position, such as a hole's center, may vary.

A standardized documentation package used, mainly in automotive supply chains, to prove that a production process can consistently make parts to specification.

An early sample part built to validate a design's fit, form, or function before committing to full production tooling and volume.

The set of inspection activities used to verify that manufactured parts meet the dimensions and tolerances called out on the drawing.

Rapidly cooling a heated metal, typically in oil or water, as part of a heat-treatment cycle to achieve a target hardness.

A Request for Quotation submitted by a buyer, along with drawings or 3D files, to obtain pricing and lead time for a manufacturing project.

A standard measurement that describes the average height variation of a machined surface's texture, used to specify surface finish requirements.

A rounded feature dimension; minimum achievable internal radii in machining are governed by the diameter of the cutting tool used.

A group of manufacturing methods, including CNC machining and 3D printing, used to quickly produce functional or visual prototypes from a CAD model.

A finishing operation that enlarges and smooths a pre-drilled hole to a precise final diameter.

Roughing removes bulk material quickly at lower precision; the finishing pass that follows takes slower, shallow cuts to achieve the final dimension and surface quality.

The amount a rotating feature, such as a shaft or bore, deviates from true circular rotation about its intended axis.

The time required to prepare a machine, fixture, and program before production of a part can begin.

A thin piece of material inserted between components to fine-tune fit, alignment, or spacing.

The rotating component of a CNC machine that holds and drives the cutting tool, or in turning, the workpiece itself.

A family of corrosion-resistant, iron-based alloys containing a minimum of 10.5% chromium, available in many grades for different strength and corrosion needs.

The chips or shavings produced as material is removed during a machining operation.

A turning process using a sliding headstock that supports the workpiece close to the cutting tool, ideal for small, high-precision, geometrically complex parts.

The process of cutting internal threads into a pre-drilled hole using a tapered, threaded cutting tool.

A lightweight, high-strength metal with excellent corrosion resistance and biocompatibility, though more difficult and costly to machine than aluminum or steel.

The permissible range of variation in a part's dimension — how far it can deviate from the nominal value while still fitting and functioning correctly.

The programmed route a cutting tool follows through a workpiece to remove material and produce the final part geometry.

The exact theoretical location a feature should occupy according to its basic dimensions; see also Positional Tolerance.

A machining process in which a workpiece rotates against a stationary cutting tool to produce cylindrical and conical shapes.

A recessed feature that cannot be reached by straight vertical tool motion, often requiring specialized tooling, EDM, or multi-axis machining.

A tolerance that allows dimensional variation in only one direction from the nominal, rather than splitting the range on either side.

A workholding device that clamps a part firmly to a machine table or vise jaws during cutting.

Manufacturing runs sized for large order quantities, optimized for the lowest achievable per-part cost.

The distance between two opposing surfaces of a part's feature; minimum recommended wall thickness varies by material, process, and part geometry.

The maximum three-dimensional space within which a CNC machine's cutting tool can physically operate.

Any method or device used to secure a workpiece during machining, including vises, fixtures, jigs, and lathe chucks.

The horizontal axis of linear travel on a CNC machine, typically representing left-right motion of the tool or table.

The horizontal axis of linear travel perpendicular to the X-axis on a CNC machine.

The stress point at which a material begins to deform permanently rather than returning to its original shape once the load is removed.

The vertical axis of linear travel on a CNC machine, typically controlling the cutting tool's depth of cut.

An electroplating process that deposits a thin, protective zinc layer onto steel parts to prevent corrosion.